Late adolescence and emerging adulthood (ages 18+) pose formidable challenges for adherence to the diabetes regimen, which contribute to poor metabolic control and increased risk for serious long-term health complications (e.g., hypoglycemia and ketoacidosis, microvascular disease, and premature mortality). Emerging adults experience new challenges as they move out of the home and the pediatric health care system. These challenges require daily regulation over one's emotion, cognition, and behavior in a way that is more independent from parents. Further, advances in developmental neuroscience reveal late adolescents are not yet able to integrate their thinking with the social and emotional demands of daily life, suggesting that these challenges occur at a time when the neurocognitive abilities needed to regulate emotion, cognition and behavior are not fully developed. There is increasing evidence that emerging adulthood is a time of high risk, but there is little research to inform how emerging adults with diabetes (or any chronic illness) make this transition successfully. The proposed research builds on our prior work that parental monitoring is beneficial for maintaining adherence across adolescence by bolstering adolescent's own self-regulatory skills (e.g., maintaining diabetes goals, preventing problems from occurring, and adjusting to problems when they do occur) and compensating for such skills when they are not yet developed. We will examine whether still developing neurocognitive abilities limit late adolescents' ability to regulate diabetes problems and adhere to the regimen, and will determine whether parental monitoring may continue to compensate for low neurocognitive abilities. In a longitudinal observational design at two sites (Utah and Texas), 250 adolescents with type 1 diabetes will be recruited in the Fall of their senior year of high school, and assessed annually for three years. In Aim 1, we identify which neurocognitive abilities (e.g., executive function, impulse control, attentional control) are needed to maintain adherence across the transition to emerging adulthood through behavioral tests and corresponding self- and parent-reports. In Aim 2, we determine how these neurocognitive abilities relate to the daily self regulation needed for optimal adherence across the transition, using two 14-day diaries conducted in the senior and post senior high year. In Aim 3, we examine whether parental monitoring across the transition to emerging adulthood benefits those with low neurocognitive abilities, and explore the ways in which parents remain able to monitor daily emerging adults' behavior (e.g., text, phone, in person). The findings will have important clinical applications for the use of family interventions tailored to the self-regulatory skills of late adolescents.